Field of the Invention
The present invention relates to an image processing apparatus and an image processing method.
Description of the Related Art
Image printing apparatuses that print an image by repetitively performing print scanning that ejects inks while relatively moving a printing head having a plurality of ejection ports with respect to a unit area of a printing medium, the ejection ports ejecting inks being arrayed, and sub scanning that conveys the printing medium are known. In such image printing apparatuses, so-called multipass printing method is known, which forms an image by performing a plurality of times of print scanning for the unit area. In a conventional multipass printing method, print data to be used in printing in a plurality of times of scanning is generated by dividing the image data into a plurality of times of scanning, using image data having one-bit information for determining ejection or non-ejection of ink for each pixel, and a plurality of mask patterns including one-bit information for determining permission or non-permission of ejection of ink for each pixel and corresponding to the plurality of times of scanning.
In an image printing apparatus that performs the above-described multipass printing method, when ejection failure of ink has occurred in a certain ejection port of the plurality of ejection ports, degradation of image quality of an image to be obtained is known. In contrast, Japanese Patent Application Laid-Open No. 2000-094662 describes replacement of information of a pixel in a mask pattern corresponding to the ejection port in which the ejection failure has occurred with information of a pixel in a mask pattern corresponding to another ejection port that can eject the ink to the same pixel region. Accordingly, even if the ejection failure is caused in the ejection port, complement printing can be performed through a different ejection port. Therefore, the degradation of the image quality can be suppressed.
Further, in recent years, generation of print data using image data having multiple-bit information for determining the number of times of ejection of ink for each pixel, and a mask pattern having multiple-bit information for determining the number of times of permission of ejection of ink for each pixel is known. By generating the print data as described above, the ink can be ejected to one pixel region a plurality of times. Japanese Patent Application Laid-Open No. 2003-175592 discloses complement printing for an ejection port in which the ejection failure has occurred, using image data having two-bit information and a mask pattern. In more detail, when the ejection failure has occurred in a certain ejection port, a pixel having the number of times of permission of ejection of ink being zero times is determined from pixels in a mask pattern corresponding to other ejection ports that can eject the ink to the same pixel region as the certain ejection port. Then, the complement printing is performed by replacing the information of the number of times of permission of ejection of ink being zero times in the pixel using information of a pixel in a mask pattern corresponding to the ejection port in which the ejection failure has occurred.
However, according to the technology described in Japanese Patent Application Laid-Open No. 2003-175592, in a form of ejecting the ink to one pixel region a plurality of times using the image data having the multiple-bit information and the mask pattern, favorably complement printing may not be able to be performed in a case where the ejection failure of an ejection port has occurred.
For example, in a print mode having a small scan amount for a unit area, or the like, there is a case of using a mask pattern that permits at least once ejection of ink for all of a plurality of pixels in mask patterns corresponding to a plurality of ejection ports that can eject an ink to the same pixel region. If the ejection failure is caused in a certain ejection port, no information of the number of times of permission of ejection of ink being zero times exists in the pixels in the mask patterns corresponding to the ejection ports that can eject an ink to the same pixel region, the replacement described in Japanese Patent Application Laid-Open No. 2000-094662 may not be able to be executed.
Further, even in a case of using a mask pattern in which the information of the number of times of permission of ejection of ink being zero times is determined for x pixels, of the plurality of pixels in the mask patterns corresponding to the plurality of ejection ports that can eject an ink to the same pixel region, favorably complement printing may not be able to be performed. In more detail, when the ejection failure is caused in y ejection ports, which is larger than X, of the plurality of ejection ports, replacement destinations of information in pixels corresponding to (y−x) ejection ports in which the ejection failure has been caused do not exist. Therefore, the replacement described in Japanese Patent Application Laid-Open No. 2000-094662 cannot be executed.